The invention relates to a measuring assembly for detecting particles of a particle stream in a gas flow path, comprising an ionization stage which has an ionization device, by which the particles to be detected can be or are ionized and with a measuring stage with a detector which detects the ionized particles of the particle stream, said detector having at least one electrode to which particles release the charge picked up on the ionization device, where the charge released can be measured via an electric resistor connected to the at least one electrode.
Measuring assemblies for detecting particles in a particle stream are widely known and used for the detection of size and/or number of particles. Known here, for example, are assemblies for carrying out gravimetric or optical particle measuring methods, but also those of the type mentioned at the beginning, in which, in a gas flow path, an ionization region or an ionization stage having an ionization device, and a measuring stage connected downstream of this stage and having a detector are arranged and formed. The detector has an electronic counting device. Here, the particle stream can, for example, be an exhaust gas flow, for example from an internal combustion engine.
The detector in known particle measuring assemblies can be formed, for example, as an electrode which is connected to the electronic counting device, while an ionization wire, for example a tungsten wire, to which high voltage is applied is arranged in the ionization region as ionization device, or a UV radiation source acts in an ionizing manner on the particle stream. The at least one electrode can be formed in the shape of a grid, to which a high-value resistor is connected. For the purpose of particle counting, the charge picked up by the particles in the ionization stage and released to the electrode is measured as a current flow over the high-value resistor.